The ultimate goal of this study is to elucidate the molecular regulation of exocrine pancreas specification and differentiation. Recent advances have been made in understanding how a pancreatic progenitor cell chooses to give rise to an exocrine versus endocrine cell fate. However, once the initial fate decision has been made, the molecular events that control exocrine specification and differentiation are largely unknown. Currently, we are aware of only a single regulatory factor, p48 that is critically required for the generation of differentiated exocrine cells. As in many other developmental systems, the molecular mechanisms that direct the development and differentiation of the exocrine pancreas are likely to involve a complex network of regulatory factors. We have recently determined that Gata4, a zinc-finger transcriptional regulatory factor is expressed in the region of the foregut endoderm that gives rise to pancreas and later becomes restricted to the exocrine acinar cells, where it physically interacts with p48. We hypothesize that Gata4 plays a critical role in the differentiation and development of the exocrine pancreas. To test this hypothesis, we propose to further characterize the expression of Gata4 during embryonic pancreas development and determine its function in the development and differentiation of the exocrine pancreas. The specific aims of this proposal are to: 1. Define the expression pattern of Gata4 in the developing exocrine pancreas. We will determine precisely when and where Gata4 is expressed in the embryonic pancreas and compare its expression patterns to known pancreatic molecular markers. 2. Verify and characterize the physical interaction between Gata4 and p48, an essential exocrine pancreas protein. We will also determine the ability of Gata4 to regulate known exocrine genes that contain Gata and p48 binding sites within in their promoter regions. 3. Identify and characterize the function of Gata4 in exocrine pancreas development. We will use antisense techniques in primary cell cultures and AR42J cells to examine the effects of loss of Gata4 on the development of the exocrine pancreas. 4. Determine the function of Gata4 in exocrine pancreas specification and differentiation in vivo. [unreadable] [unreadable]